Vitreous enamel coated objects and method of producing the same



Patented a. 17, 1944 vrrnnous ENAMEL COATED onmo'rs AND METHOD OF rnonuomo THE SAME Charles A. Getz, Glen Ellyn, and George Weidmann, Chicago, Ill.

No Drawing. Application Serial No.

19 Claims.

This invention relates to methods of applying vitreous enamels to non-ferrous metallic materials which are predominantly copper and are substantially free of lead, and the enameled objects produced by such methods.

The world of today is possessed of entirely satisfactory methods for applying vitreous enamels to both large and small surface areas of objects which are formed of ferrous metals; It has been impossible, however, to make the same assertions regarding methods for applying vitreous enamels to either large or small surface areas of objects which are formed of non-ferrous metallic materials, such as copper base alloys of the bronze group and commercially pure copper. With the market for obiects formed of such material, which have an esthetic appeal, growing at an everincreasing rate, the inability to further ornament these objects by applying an enamel coating to ,desired portions of their surfaces is a source of disappointment and embarrassment to their manufacturers.

A thorough study of the present,-unsa-tisfactory methods of applying vitreous enamels to nonferrous metallic materials, and the work produced thereby, has convinced us that these methods providing enameled surfaces which will not chip or scale oif, as a result cracks or breaks in the coating, because workers in the art have failed to recognize or understand the reasons why such cracks 'or breaks develop. that one or more of the following practices may be held responsible for the development of these defects:

1. The use of non-ferrous metallic materials which include constituents that volatilize at the high temperatures'employed in enameling processes causing the emission of gases which prevent proper fusion of the enamel binder to the metal I surface.

2. The use of non -ferrous metallic materials which do not have their various constituents uniformly mixed and/or married during'alloying and thereby develop localized spots to which the enamel binder will not properly become attached. V Y

3. The failure to use temperatures which are high enough to cause the binder to penetrate the pores of the metal to a suflicient extent and depth to provide the proper anchorage and/or to cause fusion of the binder and the enamelv the proper frit.

4. The failure to employ non-ferrous metallic November 13, 1940, 365,556

materials which will retain their structural strength when subjected to the high temperatures required for a successful enameling process.

5. The use of furnaces which will not effect uniform heating of the objects throughout the entire areas rto be enameled and which will not subject the objects, the binder, and the enamel int to the same degree of heat. 7

6. The failure to recognize the importance of very accurate temperature and time control over the steps 01f bonding the binder to the objects and fusing the enamel frit to the binder.

7. The use of a binder which, because of its method ofmanufacture and/or the particular We have determined v commercial copper, which constituents combined to produce the same, undergoes further chemical changes or reactions when subjected to the high temperatures of a; satisfactory enameling process and thereby prevents the formation of a perfect bond with the metal and the enamel. I

8. The failure to overcome the diiliculties arising from the difference in the temperature coeflicient of expansion and contraction between the metal and the enamel when heated to such high temperatures. A

9. The failure to proglde an enamel coating which is of uniform t 'ckness throughout its entire area and particularly the marginal edge portions.

The primary object of this invention is to pro videmethods of forming vitreous enamel coated metallic mateenameled objects. g A further important object of the invention is to provide methods for applying vitreous enamels to non-ferrous metallic materials, such as copper base. alloys ofthe bronze group, and pure will produce enamel coatings that will not chip or scale asa result of imperfections developed during application.

Still another tion is to provide vitreous enamel or copper objects and toprovide their coatings either of a solid or single color or 01' a mottled combination of several colors.

' Other objects and advantages of the invention will be apparent during the course of the following description.

Prior workers in the are apparently have failed important purpose of this inven-i coated bronze recognize the importance of selectlng'the J -proper types of the alloyed mixture.

is a very hard metal, and the surfaces of objects binder is being applied,

of non-ferrous metallic materials on which to apply coatings of vitreous enamel. The desire to enamel copper'base alloys of the bronze type is most pronounced. This, apparently, is due to the fact that bronzes have the desired structural strength, uncoated portions are not easily scratched or marred, and the natural color of bronze is more pleasing than pure copper.

There are available on the open market several different bronze alloys which have been developed for ordinary and special uses. Ordinary commercial bronze consists of an alloy of copper, tin, lead, and zinc. The copper, of course, is the base element, and it comprises from 88% to 89% of the entire mixture. This basic element of the alloy is noted for its resistance to corrosion and, of course, is responsible for the color characteristics of the resultant alloy. It has a relatively.

high melting point in the pure state. As casting is the usual method employed for producing bronze objects, the lead constituent is employed primarily for the purpose of adding fluidity to the .molten alloy and thus causing it to flow and more perfectly fill all portions of the mold cavity. This lead constituent comprises from 1% to 2% Neither copper nor lead formed of either of these elements are easily scratched or marred. Therefore, to give the bronze the desired degree of hardness, the zinc and tin constituents are included. Tin comprises 8% of commercial bronze, and the zinc varies from 3% to 4%, depending upon the amount of lead employed.

A bronze, to be suitable for having a perfect vitreous enamel coating applied thereto, must be able to retain its structurahstrength when subjected to temperatures as high as 1600 F. When subjected to such high temperatures, it has been I determined that the lead constituent of ordinary acteristic of lead, we have determined that this element must not be present to any substantial extent in bronze which is to be provided with a satisfactory vitreous enamel coating.

Copper, to be suitable for having a perfectvitreous enamel coating applied thereto, also must be as free of lead as is possible. So-called pure commrcial-copper contains from 0.4% to 0.1% impurities and one of these impurities is lead. However, the copper which has only the 0.1% of impurities contains such a small portion of lead that it Has been found to be satisfactory.

It has been determined that the most perfect combination of elements for producing a bronze which has the desired characteristics regarding strength and hardness and which forms a perfect base to which vitreous enamel may beapplied consists of 88% pure copper, 10% zinc, and 2% tin. Of course, when the non-ferrous metallic material to be enameled is pure copper, it constitutesl% of the object being coated. Starting with'100% copper, we have found that thecopper Imperfect alloying of these elements will produce of the alloy can be reduced as low as 80% and still obtain a structure which may be properly enameled. Depending upon the percentage of copper employed, the zinc may be varied from 12% to 0% and the tin may be varied from 8% to 0%. Therefore, the limits for an acceptable non-ferrous metallic material will be from 100% copper to a mixture which includes 80% copper, 12% zinc, and 8% tin. All conceivable combinations falling within these limits which will provide a material that will retain its structural strength at temperatures up to 1600 F. will permit proper temperatures to be employed during the enameling process.

The alloying of the copper, zinc, and tin constituents should be carefully carried out to assure a thorough mixture of these elements and.

to providea proper marriage between the same.

spots on the surfaces of objects molded therefrom. Such imperfect spots will not bond with the binder for the enamel in the same manner as or to the same extent as the perfectly. alloyed surfaces and a defect in the enameled coating' is the result.

The objects to be provided with the vitreous enamel coating are cast or molded from a bronze alloy! of the proper proportions of copper, tin, and zinc, or from pure commercial copper, and the areas to be coated are thoroughly cleaned.

- These areas should be enclosed within or surrounded by a retaining rib which is cast integrally with the body of the object. These ribs are, of course, raised above the surface to be enameled and their height should' be from 1 te /s of an inch. Ribs of greater height can be employed, but they detract from'the general appearance of the object, and they cause water to accumulate on the enameled surface if the object is placed in the open and is arranged horizontally. These raised boundaries or ribs may be of any desired cross-sectional shape, but it is preferred that their inner edges, i. e., the edges presented to the surface to be enameled, be arranged at right angles to said surface. Ihese barriers or ribs function to retain on the involved area the melted binder and enamel frit. They prevent the enamel frit from running beyond the area to be covered and thereby prevent enameled edge portions or margins of reduced thickness from being formed. In-actual use, these raised margins or ribs protect the edges of the enamel from damage as a result of roughhandling,et'c.

It will be briefly pointed out atthis time that the plate-like objects to be enameled will be molded or cast with reinforcing ribs formedon their rear faces. Preferably, these raised, reinforcing ribs will be arranged in two sets or groups that extend at right angles to each other and in parallelism with the plates. forcing. ribs will be explained in detail when the four marginal edges of the difference in the temperature coefncient of expansion and contraction between copper or bronlo and enamel is dealt with.

I eled must flrstbe conditioned, such as by cleaning, to remove all impurities, foreign matter, and

the like, therefrom. The vitreous enamel coating to be applied to the conditioned surface is attached thereto by means of a binder. It has been determined that care must be taken in selecting the binder. Many binders which have been used in the past to bond vitreous enamel to copper or copper base alloys have been found to be inc!- The'function performed by these reinobiect tobe enam- I ficient because their methods of manufacture and/or the particular constituents combined to produce the same have resulted in leaving some of the starting materials in a chemically active state. Such materials undergo a further chemical reaction, when subjected to the high temperatures employed during the enameling process. and this reaction interferes with the bonding of the binder to the base material and the fusion of the enamel frit to the binder.- We have determined that lead silicate, when prepared in accordance with one, of the following methods, is an. entirely satisfactory binder.

The lead silicate employed'as a binder between the enamel and the base material should in general be of high purity for most efficient results. As stated above, various methods may be utilized to obtain a highly pure lead silicate which is satisfactory for use in accordance with this invention.

One method of preparing lead silicate of high purity is by chemical precipitation from an aque- & ous solution of lead salts, such as lead nitrate, by the addition of alkali metal-silicate, such as sodium meta silicate. By the use of pure lead salts and pure alkali metal silicate, a high-degree of purity of the resulting precipitate of lead silicate may be secured. The precipitate may be freed of the reactants from which it is formed by extensive washing with water, preferably hot water.

{mother method of forming pure lead silicate comprises using lead salts with silicate materials. Various lead salts and various silicate materials may be used. For example, a lead oxide may, if desired, be fused with a silicic acid, or an alkali metal silicate, to form the desired lead silicate. The degree of purity of the resulting precipitate. will depend upon the purity of the lead oxides and of the silicate materials.

As another example, a lead salt containing a volatile anion radical, such as lead nitrate, lead 40 chlorate and the like, may be fused with silica or with silicates containing a "volatile cation, to thereby form a lead silicate and volatile salts. During'the fusion, the latter salts volatilize to. leave the lead silicate free of impurities. Illus- 45 trative of this is the fusion of lead nitrateand ammonium silicate to yield lead silicate and volatile ammonium nitrate.

Fluxing materials of various kinds may be employed in the fusion methods above-described. In general, however, only those fiuxing materials which will volatilize away should be employed in order that the resultant lead silicate will be of a high degree of purity.

While a pure form of leadsilicate is the desired binder in the preferred embodiment of the herein described invention, other similar materials may be employed. For example, lead oxides may be fused with silicious materials, such as quartz or flint in ground or powdered form. Borax, arsenic oxides, and alkali salts, such as sodium or potassium carbonates or nitrates, also'may be utilized in connection with the fusion reactions, if desired.

A thin coat or layer of this lead silicate binder is sifted evenly over the cleaned area of the base material which is, to receive the enamel coating. Whensifted, the binder, of course,- will be ina powdered or pulverized. condition. If de-.- sired, however, the binder may bev applied as a 7 paste or a spray. This thin coat or layer of a binder should have a thickness of from to V8- inches to'give the best'r'esults. During the first firing of the object, the binder melts and penetrates the expanded pores .of

.spotsor areas minutes.

not penetrate the pores of the is-ready to receive the Y frit in granular or powdered form is applied the heated; body -10 coating or layer of fused 3 material. The major portion of the binder should penetrate the surface portion of the object, but

it is important that a small quantity of this glasslike binder be left as a film or layer on the surface being enameled at the first firing, because it is this excess film or layer the enamel frit. It is important not to have too much excess material left on the surface, and for that reason the amount of binder applied to the surface of the object is important. The amount of binder result will depend on the firing tempefature and the duration of this first firing operation. For example, if too large a quantity of binder is used and the firing temperature is not high enough or the firing period not long enoughto cause the desired major portion of the binder to penetrate the pores of the base material, the degree and extent of penetration of the pores by the binder will not be proper, and too much of the binder will be left on the surface to be coated. The difference in the coefliciency of contraction of the binder and the enamel is rather large and weak will be formed, as a 'result of this difference if too much binder remains on the surface. If there is only a very small quantity of the binder material left on the plate, this-small amount will be thoroughly blended with or diluted by the larger quantity of enamel frit with the result that the normal difference in the 00-- which fuses with efficiency of expansion between the binder and the enamel frit will be more or less completely eliminated and no weak-spots or imperfections will be developed between the binder and the enamel.

The firing of the binder should be performed in a furnace which ture of from 1400 F. to 1500 F. The preferred temperaturein this range is 1450" F. The ob'ect is placed in the furnace and is allowed to heat up to the furnace temperature and then to remain at this temperature for from 3 to 5"minutes, de-

pending upon the'temperature'of the furnace. If f the furnace temperature is 1450 F., the object should maintained at that temperature fort 4 If the temperature of the furnace is higher, less time is required. That is to say, 3 minutes will be sufficient for a furnace temperature of 1500 F. and 5 minutes will be required for a furnace temperature of 1400 F.

It is important to employ a furnace temperature and a heating time which fall within the above noted ranges; otherwise the binder will not have the proper degree of fluidity and will base material to a desired depth or to a suificient extent. This will be apparent from the fact that the higher the temperature to which a metal porous it becomes, and if the to asufliciently high temperature, the object will,

not possess the desired degree of porosity to'permit proper penetration pf the binder.

.After the binder has been properly fired,- the metal oxide formed during the firing should be removed; Such oxide will form on exposed-surfaces of the object to which no binder has been applied. Preferably, Zhe object should be removed from the fuma e and allowed to cool be fore undertaking the removal of the oxide.

The binder coated surface of the object now enamel frit. The enamel evnly" over the to be used to obtain the desired has been heated to a temperais heated, the more "colorspfienamels may diifer one from binder and the depth of the enamel frit should be approximately from {a to V1. inch.

The object is then placed in a furnace having a temperature of from 1380 F. to 1480 F. The preferred temperature is 1430? F. The object is permitted to remain in the furnace and be sub jected to the furnace temperature for a suflicient length of time to permit the enamel frit to be properly melted and fused with the binder, which is remelted during this second firing period. The length of time required to melt and fuse the binder and the enamel frit varies with the particular enamel frit used. The periods found to be satisfactory for the various enamels, and enamel frit mixtures, which have been employed fall within a range of from /2 to 5 minutes.

In addition to using plain or solid colored reous enamels, we have developed a method of producing a mottled effect. From a distance the mottled enamel appears to be of some particular single shade or color, but upon close inspection, it

will be seen to consist of a mixture of small points or areas of a variety of colors which give life.

- sparkle, and depth to the enamel. This unusual appearance is quite pleasing and differs from plain flat colors. This mottled, or multi-colored,

vit-

The particle sizes which should be used will fall between fillmesh and 100 mesh; that is, the smallest size will be retained by 'a 100 mesh screen, while the largest size will passthrough a 60'mesh screen. With regard to these particle sizes, the coarse particles of the range give a more marked mottled effect, while the finer particles will give a less mottledeffect.

After the enamel frit is properly fired, the object is removed and allowed to air cool. The oxide, wh.ch was formed during firing. should be removed from the surfaces of the object which were not coated. If desired, lacquer, or the like, may be applied to the entire surface of the object.

Enamel has a lower coefliciency of expansion and contraction than the non-ferrous metallic materials being coated.

The filling of the pores of the front face portion ofthe plate-like object by the penetration of the prevents this front porthe enamel.

- to cause the object to bend or curve.

enamel gives somewhat the efiect of changeable silk which varies with different light exposures.

Without any intention of limiting this invention to any. particular color combinations pro-, duced by certain enamel frit mixtures, it will be explained that a wide variety of blue-gray-green color combinations so far have been used extensively. One, very pleasing combination involves several shades of green which in combination simulate the antique verdi" green that is seen on old bronze statues, etc.

' Merely by way of example, and without 'attempting to identify the .color or color effects produced in each instance,-three different typical examples of mixtures will be set forth as follows: A

Description Delicate gray-blue (opaque). Medium green (opaque). Grey (transparent).

Grey (opaque).

Description Medium green (opaque), Gre (opaque). Del cate grey-blue (opaque). 4 Grey (transparent).

Description I Medium green (opaque). Colorless (bull) (transparent).

Delicate grey-blugopaque).

. strains.

However, the above noted effect has a tendency This tendsency to bend or-curve is not desirable for two reasons: first, the appearance is object onable, and second,'it causes me hardened enamel to bend, tnerebysuolecung it to The remi'orcin'g bars formed on the rear face or back of the plate-like obfiects have been round -to overcome any tendency for them .to bend or curve. It is believed that these reiniorcing ribs prevent the bending of the plates because they cooperate with the pore-filled top surface portions to lower the coefilciency of contraction' or the entire object In other words, the back portion of the plate-like object cannot contract to its normal degree because the remforcl l r bs compel this rear, portion to contract only to the same extent as the front portion. As the porefilled r'mnt portion cannot contract to its normal degree, the rear or back portion W111 not be permitted to contract to its normal degree. The final result is that the coefificiency or contraction has approximately that of the enamel.

Regarding the type of furnace to be used for the two'firing operat.ons, the plate-like objects be supported in a horizontal plane within the heating chamber of the furnace and the heating elements should be located above and below the plates to eflect an even distribution of heat over their entire area. In other words, opposed sources of heat should be provided. for the plate-like objects, and these sources should be parallel'with the plane of the plate.

It is obvious that if the sources of heat were arranged at right angles to the plane of the platelike object, and beyond its edges, the portions of the object would heat up much faster than the central portion. This would be true even though the furnace were permitted to reach the desired temperature and the center of the 1 plate be given time to reach the proper tempera- Y ture for, under such conditions, the marginal portions would still be hotter than desired.

(a) (For the first firing, the surface to be subjecting this binder it has been determined that the penetration of the binder into the pores of the base material wil This difierence must be overcome. or a proper bond will not be provided.

destructive stresses and it is important that malning. binder binder in accordance with variations in plied to different areas of the object.

e second firing, the enamel frit is fused to the binder. To obtain the colors desired, especially the mottled colors, it is essential heat apportions,

desired effect would not be obtained.

It is very important that accurate control be maintained over the furnace temperatures during the two, firing operations and the timing of these periods. For this reason, suitable temperature andtime control devices should be applied tothe furnace.

as a film of uniform thickness over the surface,

film; and firing all portions of the object. the binder, and the enamel frit to a uniform temperature falling between 1380? F. and 148051. for a, sufficient length of time to cause thebinder film and enamel frit to melt and uniformly fuse.

. 3. A methodof producing vitreous enamel coaed objects,- comprislng applying a binder composed essentially of substantially pu're lead silicate to the cleaned surface described in order to explain invention, may be made by applying enamel frit to the reof an object formed "ofa non-ferrous metallicgmaterial consisting of thickness over 5 binder to a uniform te falling between 1400 F. and 1500 F. for from 3 to 5 minutes to cause the binder to melt and the major portion to penetrate the pores of the object leaving theremainder as a film of uniform thickness over the surface, applying enamel frit to the binder flhn, and firing all portions of the object, the binder, and the enamel frit to a uniform temperature falling between 1380" F. and 1480 F. for from to 5 minutes to cause the binder film and enamel frit to melt and uniformly fuse. 4. A method of producing vitreous enamel coated objects, comprising applying a binder composed essentially of substantially ure lead silicate to the cleaned surface of an object formed of a non-ferrous metallic material consisting of from to 1 0% copper and substantially leadfree, firing all portions of the object and the pp binder fihn, firing all por-' the binder, and the enamel temperature falling between F. for a suflicient length of time to cause the binder film and enamel frit to melt and uniformly fuse, ai

ing enamel frit to the tions of the object, frit t() a uniform silicate to the cleaned surface of an object formed of a non-ferrous metallic material consisting of from 80% to 1 0% copper and substantially leade firing a l. binderto a'uniform temperature of 1450 F. for a sufiicient length of time to cause the binder to melt and the mador portion to penetratethe pores of the object leaving the remainder as a film' of uniform thickness over the surface, applying enamel frit to th binder film, and firing enamel frit to a F. for a sufficient length of time to cause the binder film and enamel frit to melt and uniformly 7. A method of producing vitreous enamel coated obiects,- comprising applying a .binder composed essentially silicate to the cleaned surface of an object formal of a non-ferrous metallic materialconsisting of from 8 %"to 00%. copper and substantially leadfree,-fii'lng Portions of the object ,and the binder to apuniform temperatureof l450 F. for four minutes tocause the binder to melt and the major object leaving the remainder asa film of uniform the surface; appl ngenamel frit portions of the object and the of substantially pure lead portion to penetrate th pores of the to the binder film, and firing all portions of the falling between 1400 F. and 1500 F. for from object, the binder, and the enamel frit to a uni- 3 to 5 minutes to cause the binder to melt and form tem erature, of 1430" F. for 3 minutes to the major portion to penetrat the pores otthe cause the binder film and enamel frit to melt object leaving the remainder as a filmof uniform and uniformly fuse. '15 thickness over the surface, applying enamel frit to .8. A method of producing vitreous enamels the binder film. and firing all portions of the coated objects, comprising applying a binder object, the binder, and the enamel frit to a composed essentially of substantially pure leaduniform temperature falling between 1380 F. and silicate to the cleaned surface of anobject formed 1480" F. for from a to 5 minutes to cause the of a non-ferrous metallic material consisting of 10 binder film and enamel frit to. melt and unl- I from to 1 copper and substantially leadformly fuse.

free, firing all portions of the object and the 12. A method of producing vitreous enamel binder to a temperature of '1450 F. for a suflicoated copper base alloy objects, comprising apcient length of time to cause the binder to melt plying a binder composed essentially of substan and the major portion to penetrate the pores 5 tially pure lead silicate to the cleaned surface of of the object leaving the remainder as a film an object formed of a mixture consisting of 88% of uniform thickness over the surface, cooling the copper, zinc, and 2% tin, firing all portions plate, removing metallic oxides from the exposed of the object and the binder to a uniform temsurfaces of th object, applying enamel frit to perature falling between 1400? F. and 1500 F. the binderfilm, firing all portions of the object, 2 for a sufficient length of time to cause the binder the binder, and the enamel frit to a uniform to melt and the major-portion to penetrate the temperature of 1430 F. to cause the binder film pores of the object leaving the remainder as a and enamel frit to melt and uniformly fuse, air film of uniform thickness over th surface, apcooling th o j ct, and removing metallic oxides plying enamel frit to the binder him, and firing formed duringlthe second firing step all portions of the object, the binder, and the A mcthcd o du in vi r nam l enamel frit to a uniform temperature falling coated copper base alloy objects, comprising apbetween 1380 F. and 1480 F. for a sufficient plying a-binder composed essentially of substanlength of time to cause the binder film and I tially pure lead silicate to th cleaned surface of enamel frit to melt and uniformly fuse. an object formed of a mixture consisting of not 13. A method of producing vitreous enamel vless th n pp n m r h n Zi coated copper base alloy objects, comprising ap- 1 and not more than 8% tin, with the elements plying a binder composed essentially of substanso proportioned as to provide an alloy that will tially pure lead silicate to the cleaned surface of retain its structural strength at firing tempcraan object formed of a mixture consisting of 88% tures up o 1600? r firing all portions of the copper, 10% zinc, and 2% tin, firing all portions object and the binder to a uniform temperature of th object and the binder to a uniform temfalling between 1400" F. and 1500 F., applying perature falling between 1400" F. and 1500 F. enamel frit to the binder treated surface, and for from 3 1,0 5 minutes to cause the binder to firi l P ns of the object, the binder, and melt and the major portion to penetrate the pores the enamel frit to a uniform temperature fa ling of the object leaving the remainderas a film of between 1380 F. and 1480 F. uniform thickness over the surface, cooling the 10. A method of producing vitreous enamel object, removing m tallic oxides formed during oated opp b a oy Objects, comp g anfiring, applying enamel frit to the binder film, ply a i r o p ss n al y f s st firing all portions of the object, the binder, and tially pure lead silicate to the cleaned surface of the enamel frit to a uniform temperature fallihg an object formed of a mixture consisting of not between 1380" F. and 1480 F. for from V: to 5 e t n 8 pp not more than 12% zinc, minutes to cause the binder filmv and enamel and not more than 8% tin, with the elements frit to melt and uniformly fuse, air cooling the so proportioned as to provide an alloy that will object, and removing metallic oxides formed durretain its-structural strength at' firing temperaing the second firing period.

tures up to 1600" F.-, firing all portions of the 14. A method of producing vitreous enamel object and the binder to a uniform temperature coated objects, comprising applying abinder com- .falling between 1400 F. and 1500 F. for a posed essentially of substantially pure lead siliv cient length of time to cause the binder to melt gate t the cleaned surface of an object formed and the major portion to p net te e pores of of a non-ferrous metallic material consisting the object leaving the remainder as a film of of f m 80%"to 100% copper and substantially unif r th k s over thcsurfacc, app yin lead-free, firing all portions of theobioct and enamel frit to the binder film, and firing all th binder to a runiform temperature falling portions of the object, the binder, and the enambetwee 1400" F. and 1500 F., applying to the el frlt to a uniform temperature falling between binder treated surface of the Meet a layer of 1380 F. and 1480 F. for a sufilcient length of a mixture of different colored enamels as afrit, time to cause the binder film and enamel vfrit to the particle size of which will fall between r t a d un r y fus mesh and 100 mesh, and f ring all ortions of 11. A method -of producing vitreous enamel 05 the object, the binder, and the enamel frlt to coated copper base alloy objects, comprising apa uniform temperature falling between 1380 plying a binder composed essentiallyof substan- F. and 1 F.

tially pure lead silicate to the cleaned surface of 15.5 method of enameling non-ferrous metallic an object formed of a mixture consisting of not materials which are consisting of from to less than 80% copper, not more than 12% zinc, 10 copper and are substantially free of lead, and not more'than 8% tin, with the elements comprising applying abinder composed essential- 'soproportioned asto provide an alloy that will 1y of substantially-pure lead silicate to a cleaned retain its structural strength at firing tempera--' surface of the material, firing all portions of the tures up to 1600 F., firing all portions ofthe material and the binder to a uniform tempera-.

.obiectand the binder to a uniform temp ra u e 76 tutefalli g between 1400 F. and 1500 F., a

plying enamel frit to the surface of the fired binder, and firing all portions of the material, the binder, and the enamel frit to a uniform temperature falling between 1380 F. and 1480 F.

16. A method of enameling non-ferrous metallic materials which are consisting of from 80% to 100% copper and are substantially free of lead, comprising applying a binder composed essentially of substantially pure lead silicate to a cleaned surface of the material, firing all p rtions of the material and the binder to a .Liform temperature falling between 1400 F. and 1500" F. for a sufiicient length of time tocause the binder to melt and the major portion to penetrate the pores of the material leaving the remainder as a film of uniform thickness over said surface, applying enamel frit to the binder film, and firing'all portions of the material, the binder, and the enamel frit to a uniform temperature falling between 1380 F. and 1480" F. for a sufiicient length of time to cause the binder film and enamel frit to melt and uniformly fuse.

1'7. A method of enameling non-ferrous metallic materials which are consisting of from 80% to 1 0% copper and are substantially free of lead, comprising applying a binder composed essentially of substantially. pure lead silicate to a cleaned surface oflth material, firing all portions of the material and the binder to a uniform temperature falling between 1400 F. and 1500" F. for from 3 to 5 minutes to cause the binder to melt and the major portion to penetrate the pores of the material leaving the remainder as a film of uniform thickness over the surface, applying enamel frit to the binder film, and firing all portions of th material, the binder, and the enamel frit to a uniform temperature falling between 1380 F. and 1480 F. for from A; to; 5 minutes to cause the binder film and enamel frit to melt and uniformly fuse.

18. A vitreous enamel coated object, comprising a body formed. of non-ferrous metallic material consisting of from to copper and substantially lead-free, a vitreous enamel coating covering a surface area of said body, and a binder composed essentially of substantially pure lead silicate bonding the enamel coating to the body.

19. A vitreous enamel coated object, comprising a body formed of an alloy consisting of not less than 80% pure copper, not more than 12% zinc, and not more than 8% tin, avitreous enamel coating covering a surface area of said body, and a binder composed essentially 'of substantially pure lead silicate bonding the enamel coating to the body.

CHARLES A. GETZ. GEORGE WEIDMANN. 

